The use of hydrophilic polymers in the controlled release of medicaments is known. A problem with such polymers is, however, that large quantities of the hydrophilic material is often required in order to effect proper control of drug release. This is a particularly severe problem when the unit dose of the medicament is large (e.g. above about 60% by wt).
The use of anionic surfactants in solid pharmaceutical compositions is also known. Until recently, however, the presence of such surfactants was designed to facilitate fast and total release of the medicament from the composition (see, for example, Japanese Kokai 7320778 and A.A. Kassem etal, J. Drug Research, 1974, 6, 95).
U.S. Pat. No. 4,540,566 and P.B. Daly et al, Int. J. Pharm. 18, 201 (1984) describes a controlled release composition containing chlorpheniramine maleate, a cellulose ether and an anionic surfactant. However, the composition is a simple mixture and does not provide any particular advantages.